Thermal properties of an impurity immersed in a granular gas of rough hard spheres

We study in this work the dynamics of a granular impurity immersed in a low-density granular gas of identical particles. For description of the kinetics of the granular gas and the impurity particles we use the rough hard sphere collisional model. We take into account the effects of non-conservation of energy upon particle collision. We find an (approximate) analytical solution of the pertinent kinetic equations for the single-particle velocity distribution functions that reproduces reasonably well the properties of translational/rotational energy non-equipartition. We assess the accuracy of the theoretical solution by comparing with computer simulations. For this, we use two independent computer data sets, from molecular dynamics (MD) and from Direct Simulation Monte Carlo method (DSMC). Both approach well, with different degrees, the kinetic theory within a reasonable range of parameter values.Comment: 4 pages, 2 figures. Written for Powders and Grains 2017 conference proceedin

On the emergence of large and complex memory effects in nonequilibrium fluids

Control of cooling and heating processes is essential in many industrial and biological processes. In fact, the time evolution of an observable quantity may differ according to the previous history of the system. For example, a system that is being subject to cooling and then, at a given time $t_{w}$ for which the instantaneous temperature is $T(t_w)=T_{\mathrm{st}}$, is suddenly put in contact with a temperature source at $T_{\mathrm{st}}$ may continue cooling down temporarily or, on the contrary, undergo a temperature rebound. According to current knowledge, there can be only one "spurious" and small peak/low. However, our results prove that, under certain conditions, more than one extremum may appear. Specifically, we have observed regions with two extrema and a critical point with three extrema. We have also detected cases where extraordinarily large extrema are observed, as large as the order of magnitude of the stationary value of the variable of interest. We show this by studying the thermal evolution of a low density set of macroscopic particles that do not preserve kinetic energy upon collision, i.e., a granular gas. We describe the mechanism that signals in this system the emergence of these complex and large memory effects, and explain why similar observations can be expected in a variety of systems.Comment: 15 pages, 5 figure

The Role of Surface Passivation for Efficient and Photostable PbS Quantum Dot Solar Cells

Peer ReviewedPostprint (author's final draft

Luis Ortigosa, en el recuerdo (1959-2014)

2 páginasPeer reviewe

Revolution and Exploration: the English Translations of Rousseau and Humboldt by Helen Maria Williams

British author Helen Maria Williams (1759-1827) was a well-known figure in the eighteenth century literary circles, whose work was praised by Elizabeth Montagu, Samuel Johnson, Dorothy and William Wordsworth, Mary Wollstonecraft, Hester Piozzi or Alexander von Humboldt.  In her early poems  Edwin and Eltruda (1782), An Ode to the Peace (1783) and Peru (1784), Williams starts to reveal her political tendencies by appealing to strong empathic feelings as a key to social and political transformation. As a result of her interest in politics, she travelled to France in 1790 and published her most acclaimed work Letters from France (1790). However, the rest of her production has received little critical attention by modern scholars, who have overlooked her involvement in translation. Williams’ only extant novel, Julia (1790) is in fact a creative translation of Rousseau’s Julie ou La Nouvelle Héloïse (1761), in which Williams includes poems that evidence her interest in revolutionary politics. Four years later, she translated Bernardin de Saint Pierre’s Paul et Virginie, while she was imprisoned in Paris. While translating novels was regarded as a respectable exercise for women writers, Williams challenges gender assumptions by translating Researches (1814) and the seven volumes of Personal Narrative (1814-1829), which had been produced by one of the most influential eighteenth century scientists, Alexander von Humboldt. This article interrogates how Williams makes use of translation to access areas of knowledge traditionally restricted to men, such as philosophy, politics and science. For this purpose, I will focus on her translations of the work of two leading intellectual figures of the eighteenth century,  Rousseau and Von Humboldt

Lattice models for granular-like velocity fields: Hydrodynamic limit

A recently introduced model describing -on a 1d lattice- the velocity field of a granular fluid is discussed in detail. The dynamics of the velocity field occurs through next-neighbours inelastic collisions which conserve momentum but dissipate energy. The dynamics can be described by a stochastic equation in full phase space, or through the corresponding Master Equation for the time evolution of the probability distribution. In the hydrodynamic limit, equations for the average velocity and temperature fields with fluctuating currents are derived, which are analogous to those of granular fluids when restricted to the shear modes. Therefore, the homogeneous cooling state, with its linear instability, and other relevant regimes such as the uniform shear flow and the Couette flow states are described. The evolution in time and space of the single particle probability distribution, in all those regimes, is also discussed, showing that the local equilibrium is not valid in general. The noise for the momentum and energy currents, which are correlated, are white and Gaussian. The same is true for the noise of the energy sink, which is usually negligible

Effects of European Common Agricultural Policy and Regional Policy on the Socioeconomic Development of the Central Pyrenees, Spain

8 páginas, 6 tablas.Although the European Union has invested important subsidies in European mountain areas since the 1980s, the influence of these subsidies on the economy and society of these regions has so far not been analyzed. For this reason, we conducted a quantitative analysis of the effects of public policies on the development of the Central Pyrenees from 1986 to 2001. During this period, around €170 million (US$ 226.3 million) was invested in development of the Central Pyrenees through the Common Agricultural Policy and Regional Policy. However, in our analysis of correlations between several socioeconomic factors, we found that the number of inhabitants, farms, and employees in the primary and secondary sectors had decreased, while the tourist sector was becoming a major part of the economy. These findings seem to indicate that public policies had little effect; but although our analyses revealed that the various subsidies did little to promote structural improvement, they were important for supporting inhabitants (for example farmers) in the Pyrenees, because they are a form of complementary income, they allow communities to maintain farming activities, and they favor small enterprises linked to tourist activities—thus preventing depopulation. As the Pyrenees have little capacity for endogenous development, we argue that the current public policies should be maintained for the foreseeable future.This work has been supported by the following projects: “Processes and sediment balances at different spatial scales in Mediterranean environments: Effects of climate fluctuations and land use changes” (CGL2006- 11619/HID), and “Vegetation recovery and erosion on fire-affected lands. Integrated analysis of fire severity and environmental parameters using remote sensing and GIS” (CGL2005-04863/CLI), funded by the CICYT.Peer reviewe